1. Field of the Invention
The invention generally relates to wireless communication technologies, and more particularly, to code sequence generation systems and methods for providing a padded code sequence.
2. Description of the Related Art
For a wireless communication environment utilizing Orthogonal Frequency-Division Multiplexing (OFDM) technology. Transmission data is carried in a plurality of orthogonal sub-carriers. For example, the transmission data is divided into multiple groups and each group is mapped into one modulation symbol, and these modulation symbols are further placed on these sub-carriers. Subsequently, transmitter performs Fast Fourier Transform (FFT) and produces time-domain samples, and then the transmitter performs digital to analog (D/A) conversion and generates time-domain continuous waveform. Then the transmitter performs up-conversion on the produced time-domain waveform to a carrier. Single carrier OFDM (SC-OFDM) is a similar technology to the OFDM. The transmitter performs FFT on the modulation symbols, and allocates the transformed samples on frequency domain. Transmitter continues with performing inversed FFT (IFFT), and then performing the D/A conversion and up-covert to a carrier. The OFDM technology is widely adopted in a large number of wireless communication standards, such as IEEE 802.11a/g, the Ultra-WideBand (UWB), the Worldwide Interoperability for Microwave Access (WiMAX), 3GPP Long Term Evolution (LTE), etc. SC-OFDM is applied in the uplink for the 3GPP LTE.
Zadoff-Chu code features low peak to average power ratio, zero cross-correlation, low complexity receiver, etc. The LTE has adopted this code in synchronization channel, uplink control channel, etc. There are some other codes with similar features such as generalized chirp-like code, CAZAC sequence. Within a set of Zadoff-Chu code, the codes are orthogonal and provide excellent detection probability if match detection is used. However, when the differential detection is applied, this code is not optimal.